https://github.com/tc39/proposal-temporal/issues/1753 records the
consensus reached at the October 2021 TC39 meeting to disallow "-000000"
as an extended year, both in Date.parse and Temporal. This adds tests for
the Temporal part of that.
This requires a few adjustments of time zone names and offsets in some
places. The only named time zone that is required to be supported by an
implementation not supporting ECMA-402 is "UTC".
